A simplified thermal circuit model of permanent magnet machine part I: Model and parameters

For evaluate the thermal behavior of a permanent magnet motor under different types of losses and various loss distributions, a simplified thermal circuit is proposed. This topic is split into two separated papers. The first paper focuses on the building of the model and to evaluate key parameters. The experiment to verify the accuracy of the model is presented in a separated paper. The method proposed in the paper takes the iron losses as well as the copper losses distribution into account. Thermal resistant are the only elements in the circuit, thus can be used to evaluate the static temperature rise in an electrical machine. Only seven elements are used in the model, much lesser those in the literature. All the expressions of the thermal resistance are given in the paper, which relates the temperature rise with the machine dimensions and material properties. What´s more, a method to model the gap between the water jacket and the stator core is given, which makes the model more accurate when calculating the temperature rise of a machine using water-cooling.